Tire-gage



A. B. LOW.

TIRE GAGE.

APPllc/Tlon Hummm. l2. 191s.

1,388,275.. Patented Aug. 23, 1921.

2 SHEETS-SHEET l.

.f2 faf .33 33 A. B. LOW.

TIRE GAGE.

APPLICATION FILED APn.12. 191s.

1,388,275. Pamd Aug. 23,1921.

ARTHUR B. LOW, 0F D'ENVERVCOLORADO.

TIRE-GAGE.

speculation o f Letters Patent. Patented Aug. 23, 1921.

Application filed April 12, 1918. Serial No. 228,251.

To all whom it may concern ,Be itl known that I, ARTHUR B. Low, a citizen ofthe United States, residing at the city and county of Denver and State of Colorado, have invented certain new and Auseful Improvements in Tire-Gages; and I do declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the characters of reference marked thereon, which form a part of this specification.

My invention relates to improvements in gages adapted for measuring fluid pressure, being more particularly intended for measuring the pressure in pneumatic tires of the class employed in connection with automobiles, bicycles, motorcycles, etc.

My object is to provide a gage, the bar of which is projected outwardly by the action of the fluid pressure on a plunger'connected with'the inner extremity of the gage bar and on which the fluid acts, the plunger being retarded-by friction alone, which friction gradually increases as the plunger moves outwardly, thus making it practicable to ascertain from suitable characters formed on the gage bar and gradually increasing as they extend inwardly from the outer eX- tremity of the bar, the pressure within the tireor .other receptacle containing fluid as air or other gas under pressure.

The structure generally speaking consists of a tube through one extremity of which the gage bar projects a short distance normally, the. entire numbered area` however, of the bar being normally concealed. To the inner extremity of they bar is secured the plunger whose outward movement is frictionally retarded, the shape of the tube being constructed to produce this result. Other provision within the tube may also be made to effect the same result. The opposite extremity of the tube from that through which the outer extremity of the gage bar protrudes, is constructed topermit the access of air f-rom the tube of the tire through the medium of one or more perforations which are surrounded by such material as rubber, as will make it practicable to seal the casing of the tirevalve while the part of the gage in which the perforations are formed acts upon the valve stem to unseat the valve pieces of the tire valve. The part of the device containing the perforations is preferably of metal which may be recessed or chamberedr, surrounding its central part to receive the elastic material adapted to seal the casing of the tire valve during` the use of the gage as just explained.

Any suitable provision may be made for gradually and uniformly increasing the degree of friction as the plunger forces the gage bar outwardly, the plunger'itself being acted on by the pressure of the fluid to be measured. 4The plunger is preferably perforated in order to allow the fluid pressure to pass inwardly and equalize on both sides of the plunger except as to the cross sectional area of the gage bar. This is pre erable for a number of reasons which will. e hereinafter fully set forth. j

Having briefly outlined my improvement I will proceed to describe the same in detail, reference being made to the accompanying drawing in which is illustrated several embodiments thereof. In this drawing:

Figure l is a central longitudinal section of my improved gage.

Fig. 2 is a cross section taken on the line 2 2, Fig. l.

Fig. 3 is a fragmentary, detail view of the gage bar showing the plunger attached.

Fig. 4 is a fragmentary sectional view of the device shown on a somewhat larger scale and with a slightly modified form of plunger.

Fig. 5 is a section of the device similar to Fig. 1, but showing a modified form of structure.

Fig. 6 is a cross section taken on the line 6 6, Fig. 5.

Fig. 7 is a central longitudinal section illustrating another form of the gage, the gage bar being hollow and partly broken away Fig. 8 is a cross section taken on the line 8-8, Fig. 7.

Fig. 9 is a central longitudinal section of another form of the gage.

Fig. 10 is an end elevation looking in the direction of arrows 10, Fig. 9. Y

Fig. 11 is a similar view looking in the direction of arrows 11, Fig. 9.

Fig. 12 is a view of Fig. 9 looking in the vdirection of arrows 12.

Fig. 13 is a central longitudinal sectionrof the gage showing another form of construc tion.

Fig. 14 is. a section taken on the line 14-14, Fig. 13 shown on a larger scale.

Figs. 17 and 18 are central longitudinal sections of the gage showing other and distinctforms of construction. s

Fig. 19 is a section taken on the line 19-19, Fig. 18.

Fig. 20 is a longitudinal section showing another form of construction.

Fig. 21 is a fragmentary perspective view of the gage bar and plunger illustrating the form disclosed in Fig. 20.`

Fig. 22 is a longitudinal section showing another form of the device.

Fig. 23 is a cross section taken on the line 23-23, Fig. 22, the parts being shown on` a larger scale.

Fig. 24'is a fragmentary perspective viewl 4in detail of the gage bar and showing a metal armored form of plunger.

Fig. 25 is a fragmentary perspective view in detail on a larger scale, showing one of the elementsof the metal armor of Fig. 24.

Fig. 26 is a fragmentary sectional view in perspective ofthe upper part of the gage tube in one form of construction.

Fig. 27 is a perspective view of one member of the metal armor for the compressible material in the'form of construction shown in Figs. 22 and 23 showing also the two disks in which, the metal armor members are anchored and guided.

The same reference characters indicate the sameparts in all the views.

Let the numeral 5 designate a tube which is depressed longitudinally on two opposite sides, the depressions gradually increasing in degree from the inner extremity 6 tol the outer extremity 7 ofthe' device, it being understood that the terms innerf and outer are employed for convenience of description. These depressions which I will designate by the numeral 8 are inwardly, and their ob]ect 1s to gradually increase vthe frictional resistance of a plunger 9 as the latter moves outwardly in the tube under the influence of fluid under pressure which enters through one or more perforations 10, Fig. 4, formed in the outer portion of a cupshaped `part 12 formed in a disk 4 which closes the inner extremity of the tube 5, a cap 13 being threaded upon the tube outside of vthe disk 4 and retaining in place a quantity of compressible material 14 as rubber, the cap having an opening V15 which is somewhat larger than the part 12 of the disk in order to allow room for the casing of the tire valve to seal the latter during the use ofthe gage. The cup-shaped part 12 is provided interiorly'with a quantity 16 of some suitable material adapted to form an air filter, whereby the air is prevented from carrying solid particles of appreciable size into the tube of the gage.` It will be noted in Figs. 1 and 4 two perforations 10 are shown. The object of a plurality of perforationsis to make it impossible for both perforations to be sealed by the outer extremity of the stem of the tirevalve during the use of the gage. It will be understood that as the perforated 4part of the cup-shaped portion of the disk is applied to the outer extremity of the stem of the tire valve, the valve piece will be unseated allowing the air to enter the tube .5 through one or both of the perforations 10. In this form .of the device the plunger 9 is constructed of some compressible material as rubber or rubber compound, the plunger beingI secured to the gage bar 17 by passing a reduced part 18 of the bar through the center of the plunger and applying a nut 19 to the exposed threaded end of the said part. In this form exteriorly concave washers 20 and 21 are applied to the plunger on opposite sides, thus making it practicable to regulate to some extent the size of the elastic or compressible plunger. It will be understood that as the nut 19 is tightened there will be a tendency to expand the plungercircumferentially. This plunger either in its construction or in the manner of its connection with the gage bar must be fashioned to allow the fiuid under pressure as air from the tire to pass into the chamber of the tube beyond the plunger or on the opposite side thereof from its entrance, whereby the effective action of the compressed fluid on the plunger `for fluid registering purposes is only upon an area of the plunger i equal tothe cross section of the gage bar 17. This is an important feature since if the plunger sealed vthe st'ructure against the entrance of air to the side of the plunger o posite its entrance,lthe pressure would e greater than desired and would require fric- 11E tional resistance of too great magnitude, with the result that the frictionally engaging elements would be subjected to greater wear than is desirable.

Again, under the conditions stated, un- 124 due pressureA on the outer end 'of the gage bar would be necessary in order to return the latter to its normal position after each fluid registering act. As showniin Figi, they outer extremity of the tube is sealed 12` around an opening 22 through which the gage bar passes by a gasket or cup-leather 23 which extends inwardly a short distance around the gage bar shown at 24, the air pressure within the tube serving to seal the 13 lchamber around the gage bar against the escape of fluid. This gasket or cup-leather is held in place in the outer extremity of the tube by an expansion member or sprlng ring 28. The outer extremity of the gage bar is preferably reducedv in slze, as shown at 25, leaving a point normally projecting beyond the tube which may be utilized in releasing the valve of the tire in case the valve piece is stuck. This part 25 may also be advantageously employed in various other relations.v

In using the form of device illustrated in Figs. 1 and .4 it will be understood that in the first instance the inner extremity of the gage is applied to the open end of the casing of the tire valve, which open end will engage the compressible or elastic material 14 around the cup-shaped part 12, while the perforated portion of the part 12 will act upon the valve stem to unseat the valve. As the outer end of the casing of the tire valve is sealed by virtue of its engagement with the elastic material 14, the air released by unseating the valve will pass through one or both of the perforations 10 through the air filter 16 into the tube and into engagement with the plunger 9, the fluid passing also beyond the plunger so that the pressure on both sides of the plunger is equalized, except as to an area equal to the cross section of the gage bar. The plunger and gage bar will then be moved outwardly under the influence of the air pressure, the said movement being frictionally retarded, the friction gradually increasing, due to thefact that the inwardly bent or upset parts 8 of the tube gradually increase in degree from the inner to the outer extremity of the tube. The gage bar, as illustrated in the drawing, `is provided with numbers increasing by a common difference of ten, from 20 near the outer' extremity of the bar to near the inner extremity thereof. The instrument will be properly calibrated and the figures will be placed on the bar in accordance with such calibration.

While in Figs. 1 and 2 the tube is provided with two depressions or inwardly offset wedge-shaped parts, it will be understood that a greater number of these parts may be employed if desired. It should also be understood that various other constructions may be resorted to, some of which are set lforth in the drawing in order to obtain the necessary gradual increase inV friction as the plunger moves outwardly in the tube under the influence ofthe air pressure of the' tire tube or other receptacle containing the fluid pressure to be lmeasured or registered.

In Fig. 3 exteriorly convex washers 26 and 27 are em loyed on opposite sides of the plunger, t eir object being to gradually draw in the edges of the periphery of the plunger as the nut is tightened. In this way a slight contraction of the plunger circum- 'ferentially, particularly as to the edges, may be attained.

In the form of construction shown vin Fi 5, the base or inner extremity of the tube 1s provided with a cap 29 of somewhat different construction than that shown in the other views heretofore described. The inner extremity of the tube :enters a circumferential groove 30 formed in the base and is secured in place. A circular cavity annularly arranged within the outer part of the cap contains'a quantity 31 of elastic or compressible material as rubber, which is utilized in sealing the outer extremity of the casing (not shown) of the tire valve, while the central part 32 of the cap forms a receptacle for the air filtering material 16, the part of the cap which retains the filtering material in place having perforations 33. The elastic material 31 is exteriorly exposed, but will be packed or forced into its annular cavity in such a manner that it will be retained sufliciently securely for all practical purposes.

In the form of construction shown 'in Figs. 'and 6 the plunger is composed of a metal disk 34 which is secured to the inner extremity of the gage bar 36 by a screw 35. In this case the tube 37 is .cylindrical in shape and attached to allow the circular plunger to move freely therein, but the gage bar tapers from its inner extremity outwardly and passes through an opening formed in a quantity of compressible or elas- 100 tic material 38 held in the outer extremity of the tube by a ring 39, the outer end of the tube having a relatively large gage bar opening 40 to make room for the gradually increasing cross section of the gage bar as the latter moves outwardly. In this case, the friction necessar for the proper performance of the function of the device is obtained by the contact of the wedge-shaped or tapering gage bar with the compressible or elastic material 38. In this case a perforation 4l is formed in the plunger disk 34 to allow the fluid under vpressure to pass to the opposite side of the plunger Ifrom the inlet side.

In the form of construction shown in Figs. 7 and 8 the construction of the tube and the exterior tapering shape of the gage bar are substantially'the same as shown 1n Figs. 5 and 6, but in Figs. 7 and 8 the gage bar is hollow and devoid of a separate plun- 1'20 ger.' its lower part extending into the cap and having an outwardly turned circumferential flange 42, the gage bar in its entirety being designated by the numeral 43. In this case the air under pressure enters the cap through perforations 33 as in Fig; `5 and passes into a hollow gage bar whose cavity is open at the bottom and closed at the top. The flange is perforated, as shown at 44, to allow the pressure to equalize on both sides vthe ellipsoidal form increasing from its 1nner to its outer extremity. In this form of y construction the plunger 9 is compressible or elastic and the gradually increasing friction results from the continual change of shape of the normally circular plunger into the ellipsoidal shape of increasing degree as the plunger moves outwardly under the infiuence of the fiuid pressure, the lower or inner extremity of the tube being substantially the same as shown in Fig. 1.

In Figs. 13 to 15 inclusive, the plunger 46 is rigid, being preferably composed of'metal and is perforatedas shown at 47 to receive the arms 48 of a spring yoke, the said arms gradually approaching eachother as they extend outwardly from the base, their outer extremities being connected by a semicircular part 49. As the plunger moves outwardly -under the influence of the fluid pressure, the

arms 48 are separated by virtue of the .ielding capacity of the part 49, such part o ering the resistance which results in the necessary increasing friction between the plunger and the arms 48 of the yoke.

I n the form of construction shown in Fig. 17, the tube 50 constitutes the frustum of a cone and gradually tapers from its inner to its outer extremity, while the plunger 9- which is of the same form as shown in Fig. 1 is elastic or compressible and the necessary lincrease in friction is obtained between the contact surfaces of the plunger and the engaging inner surface of the tapering tube.

In the form shown in Figs.v 18 and 19 the tube 51is cylindrical throughout its length and there is arranged-therein a quantity of compressible or elastic material 53 which is open to receive the rigid plunger 52. The opening or cavity gradually tapers from the inner toward the outer extremity elastic material 53, whereby the necessary increase in friction is obtained as the plunger moves outwardly under the influence of the fluid under pressure. IIn this form of construction the plunger is provided with a perforation 54; and a disk 55 which engages the inner extremity of the tube surrounded by the cap 56, the disk having "a central projection 57 which passes through but does not fill an opening 58 formed in a washer 59 preferably composed of rubber and forming an elastic seat for the outer extremity of the tube or casing of the. tire valve for sealing purposes. In this case the projection 57 acts upon the stem of the tire valve to unseat of the.

the valve piece while the air under pressure passes through the opening 58 around the projection 57 and thence through a layer 60 of felt or other suitable filtering material after which it enters the chamber 61 throu h a. perforation 62. As the plunger 52 and t e gage bar move outwardly, the plunger compresses the elastic material 53 and as the thickness of this material increases from the inner to the outer extremity of the tube the friction is correspondingly increased, thus giving the desired result on the principle of all other forms ofmy improved device. In this case the elastic material 53 within the tube itself constitutes a seal at the outer extremity of the tube around the gage bar.

Inv the form of construction shown in Figs. 22, 23 and 27 the quantity of elastic or compressible material 63 is arranged within the tube 64 which is cylindrical in shape.

-The elastic material 63 is substantially of the same shape as in Fig. 18, being comparatively thin at the inner extremity ofthe tube and increasing in thickness toward .its outer extremity. At the outer and inner extremlties of the elastic or compressible material 63 are respectively arran ed disks 65 and 66 which form anchors or the opposite extremities of a series of tapering plates 76 which form a metal armor for the elastic material 63, whereby the metal plunger 67 as it moves outwardly in the gradually minishing cavity acts upon the plates 76 thus bringing two metal surfaces in contact with each other for frictional purposes. The opposite extremities of the armor plates 76 are` respectively provided with reduced projections 68 and 69. The projections 68 enage lradial slots 70- formed 1in the outer disk 65 while the projections 69 engage anchoring recesses 71 formed in the disk 66. In this form of construction the air will enter the inner extremity of the tube in the usual manner and act upon which maybe perforated as shown in other forms, to allow the air or other iuid to occupy the outwardly tapering cavity on both sides of the plunger. As the plunger moves outwardly the armor plates 7 6-gradually expand or open against the backlng of compressible material 63/ between the armor plates and the inner surface of the tube. In

the plunger 67 this way the necessary increase in friction is mally sufficiently open to slip freely over the edge of the elastic plunger 78 but are afterward clenched by pressing their inner extremities toward each other sufficiently to hold them securely in place upon the elastic material. l

In the form shown in Figs. 20 and 21, the tube 81 tapers from its inner to its outer eX- tremity and the plunger 82 which is secured to the gage bar 17 is reduced in size so that it shall not be larger than the smallest inner diameter of the tube: aThis plunger member is perforated to receive the lower extremity of the gage bar and to the latter, below the plunger, is attached by a nut 83 a yielding yoke 84 having a number of spring arms 85 which engage the tapering inner surface of the tube and the pressure on these arms gradually increases as the plunger moves outwardly in the tube, whereby the necessary increasing frictional resistance results in order to carry out the principle of my improvement.

From the foregoing explanation the operation of the various forms of my improvement in a. general Way will undoubtedly be clearly understood; and while I have shown .a number of forms or embodiments of the invention, it is evident that the invention embraces a eat many forms other than disclosed. I? det-ails of construction except as set forth in the appended claims.

In my improved device,'I prefer to employ a suitable lubricant for the surfaces of the frictionally contacting parts in order to prevent possible sticking of the parts and in order to promote uniformity in the increase of the friction during the outward movement of the plunger and gage bar. The importance of some lubricating substance is particularly great Where rubber or its compounds or similar elastic or compressible material is employed as one of the friction sur faces. This lubricant may vconsist of any suitable material either in powdered form, in liuluid or in semi-liquid form. Powdered grap ite or other anti-frictional material in powdered form, as plumbago, mica, pow'- dered aluminum or soapstone may be advantageously employed. If used as a dry powder within the chamber or cavity in which the plunger travels, provision should be made to prevent its working into any vof the orifices of the device which must be kept open for the passage of air. This function may be accomplished by a layer of felt or other suitably porous material adapted to form an air fi in Fig. 18, the element 58 forming a protection against the passage of the powdered materia-l into the opening or orifice through which the air under pressure enters the instrument.

However, instead of using the powdered ence, the invention 1s not limited ,to-

ter. This feature is illustrated;

lubricating substance in dry form it may be mixed with glycerin or other suitable liquid in order to prevent its sifting into the orifices of the device. It must be understood, however, that the invention is not limited to the employment of the lubricant specified since any suitable or desirable substance in any convenient or appropriate form may be used. It is also evident that the lubricant feature may be omitted altogether Without in any way departing from the spirit of the invention.

Having thus described my invention what I claim is:

' 1. A tire gage, comprising a tubular member open at one end to receive fiuid under pressure and having a cavity therein, a plunger movable in said cavity and in frictional engagement with the member, the'two parts being constructed and arrangedv to gradually increase the friction as the plunger moves from the open end in predetermined degree having definite and predetermined relation to the extent of movement, and a gage bar on which said plunger is mounted, there being a; passage connecting the portions of said cavity on opposite sides of the plu'nger, whereby'the effective pressure area is equal bar.

' 2. A tire gage comprising a tubular member open at one end to receive fluid under pressure, a plunger member movable in said tubular member and in frictional engagement therewith, a gage bar connected to said plunger and movable therewith, and means for retarding the travel of the plunger and gage bar from said open end by gradually increasing the friction in predetermined degree having predetermined relation tothe extent of movement under increase of pressure.

3. A gage of the class described comp-rising a tubular member, a plunger therein, a gage bar connected to said plunger, said bar having a graduated part, the tubular mem-l ber being open at its inner end for the en.- trance of fluid and at the outer end for the reception of the graduated part of the said gage bar, the latter being arranged to4 be actuated by the fluid under pressure, the device including means for retarding the outward travel of the said plunger by graduall increasing the friction in predetermin degree having predetermined relation to the extent of movement under increase of pressure.

4. The combination of a tubular member, a plunger movable therein, a gage bar connected to said plunger, the tubular member being open at one end for the entrance of fluid under pressure and at the other end for the projection of the -gage bar, and means for retarding the travel. of the plunger from said "open end by gradually increasingfriction in predetermined degree having predeonly to that of a cross section of the gage member, and a member coperating with the tube to` gradually increase the friction as the said gage means moves in the tube from its open end in predetermined degree having predetermined relation to the extent of movement under increase of pressure.

6. A device of the class described comprising a tubular means, and gage means including la bar, said gage means being movable in said tubular means in frictional contact therewith, said parts being shaped to cause the friction to continually increase as the gage means moves from the fluid receiving end of the tubular means, one of said means being yielding and the other rigid, the tubular means bemg open at one end to receive fluid under pressure and at the opposite end for the projection of the gage bar.

7. The combination of a tube open at one end to receive fluid under pressure, a gage bar and a plunger secured to the inner extremity of the bar and in frictional contact with the tube, which is shaped by having its sectional area decrease from said open end to the other to increase the friction as the plunger moves from said open end.

8. In combination ina tire gage, a hollow member open at one end to receive fluid under pressure, a gage bar member and a friction member, the transverse dimensions of one of said members being gradually varied from one end of the device to the other to increase friction gradually as the friction member moves from Said open end.

9. The combination of a tube open at one end to receive fluid under pressure, a gage bar and a plunger secured to the inner extremity of the bar and in frictional contact With the tube which is shaped to increase the friction as the plunger moves therein from said open end in predetermined degree having predetermined relation to the extent of travel.

10. The combination of atube open at one endto receive fluid under pressure, a gage bar extending Within the tube and a plunger secured to the inner extremity of the bar and in frictional contact with the tube Which'is shaped to increase the friction as the plunger moves from said open end, the plunger being perforated to allow the motive fluid to pass from one side of the plunger to the other to occupy the tube on both sides of the plunger.

11. The combination of a tube having an opening at one end to receive fluid under pressure, a gage bar extending Within the tube and a plunger secured to the inner extremity of the bar and in frictional contact with the tube, the latter having a longitudinal indenture in its outer face increasing in depth from the fluid receiving end toward the opposite end of the tube, forming an interior rib of counterpart shape.

12. The combination of a tube having an opening at one end to receive fluid under pressure, a gage bar extending Within the tube and a compressible plunger 'secured to the inner extremity of the bar, the tube being formed with an interiorly projecting longitudinally disposed area increasing in depth from its fluid receiving end toward its outer extremity and engaging the plunger in frictional relation.

13. The c'ombinationof a tube having an opening at one end to receive fluid under pressure, a gage bar extending Within the tube, a compressible plunger secured to the inner extremity of the bar, andlongitudinally disposed means in the tube increasing in transverse dimensions from the fluid receiving end to the other and engaging the plunger in frictional relation to increase the friction as the plunger moves from the fluid receiving end.

14. A device of the class described comprising a tubular means and gage means, the latter consisting of a gage bar proper and a plunger in fractional contact with the tubular means, the gage bar part having a reduced extremity passing through the plunger part, metal Washers applied to the plunger part on opposite sides and a nut threaded upon the reduced part of the gage bar for securing the parts in coperative relation, the Washers beingshaped to change the form of the plunger part as the said nut is adjusted, the plunger part being sufficiently yielding for the purpose.

15. A gage of the class described comrisin a 4tubular member, a plunger therein including a gage bar proper, the tubular member being open at its inner end for the entrance of fluid and at the outer end for the passage of the gage bar part of the plunger member, the latter being arranged to be actuated by the fluid under pressure, the tubular member being shaped to retard the outward travel ofthe plunger member by gradually increasing the friction, and means for sealing the outer extremity of the tubular member aroundv the protruding gage bar.

16.1 The comblnation of a tube having one end open to receive fluid under pressure, a gage bar, and a plunger secured to the inner extremity of the its sectional area decrease from said open bar and in frictional contact with the tube which is shaped by having l end to the other to increase the friction as the plun er moves from said open end, the plunger eing perforated to allow the motive fluid to pass from one side thereof to the other to occupy the tube on both sides of the plunger. v

17. The combination of a tube having one end open to receive'fluid under pressure, a gage bar extending within the tube and a plunger secured to the inner extremity of the bar and in frictional contact with the tube, the tube being shaped by having its transverse dimensions varying from one end to the other to increase the friction as the plunger moves from said open end. l

18. The combination of a tube having one end open to receive fluid under pressure,` a gage barextending within the tube and a plunger secured to the inner extremity of the bar and in frictional contact with the tube, the tube being shaped by having its transverse dimensions 'varying from one end to the other to increase the frictionjas the plunger moves from said open end, the plunger being perforated to allow the motive fluid to pass from one side thereof to the other to occupy the tube cavity on both sides of the plunger.

19. A device of the class described, comprising tubular means having an opening at one end to receive fluid under pressure and gage means movable therein and in f rictional contact therewith, the relative sizes and shapes of the two means being such that the friction increases continually in predetermined degree having predetermined relation to the movement of the gage means from the fluid receiving end under increase in pressure.

20. A device of the class described comprising a hollow member having an opening at one end to receive fluid under pressure, a gage bar movable therein, a plunger connected to said gage bar and friction means coperating with 'said plunger to increase the friction in a predetermined degree in accordance with the movement of said plunger l from the fluid receiving end under increase in pressure.

In testimony whereof I affix my signature.

ARTHUR B. Low. 

